swift - 位置管理器位置

Question

我有一个列表，其中填充了来自 API 的数据。所以基本上过程是这样的:

当用户打开应用程序时，我会执行以下操作:

if CLLocationManager.locationServicesEnabled() {
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.distanceFilter = 20
        locationManager.startUpdatingLocation()
    }

然后在我的 func locationManager(manager: CLLocationManager, didUpdateLocationslocations: [CLLocation]) 中，我调用 API 来获取数据。

但问题是 func locationManager(manager: CLLocationManager, didUpdateLocationslocations: [CLLocation]) 有时最多可以调用 5-6 次，因此会有大量 API 调用，如果我只获得一个位置，很有可能我获得的位置可能远离用户。

有什么想法可以解决这个问题吗？我基本上想要最好的位置并进行尽可能少的 API 调用，最好是这样。

Answer 1

基本上，如果您想避免在 func locationManager(manager: CLLocationManager, didUpdateLocationslocations: [CLLocation]) 处调用 API，您需要考虑一些控件:

• 创建接收位置之间的时间间隔
• “改进”您的 horizo​​ntalAccuracy 和 distanceFilter 值

请记住，您始终需要避免:

• 避免零位置
• 位置无效
• 位置无效
• 位置无序
• 缓存位置(在启动 locationManager 之前)

代码示例:

protocol MyLocationManagerDelegate {
    func locationControllerDidUpdateLocation(location: CLLocation)
}

final class MyLocationManager: NSObject, CLLocationManagerDelegate {

    var oldLocation: CLLocation?
    let kTimeFilter = Double(10)                  //avoid locations for each kTimeFilter seconds
    let kValidDistanceToOldLocation = Double(100)  //avoid location less than kValidDistanceToOldLocation meters
    var startDate: NSDate?
    var delegate: MyLocationManagerDelegate?


    func isValidLocation(newLocation newLocation: CLLocation?, oldLocation: CLLocation?) -> Bool {

        // avoid nil locations
        if newLocation == nil {
            return false
        }

        //avoid invalid locations
        if newLocation!.coordinate.latitude == 0 || newLocation!.coordinate.longitude == 0 {
            return false
        }

        //avoid invalid locations
        if (newLocation!.horizontalAccuracy < 0){
            return false
        }

        if oldLocation != nil {

            let distance = newLocation!.distanceFromLocation(oldLocation!)

            if fabs(distance) < kValidDistanceToOldLocation {
                return false
            }

            //avoid out-of-order location.
            let secondsSinceLastPoint = newLocation!.timestamp.timeIntervalSinceDate(oldLocation!.timestamp)
            if secondsSinceLastPoint < 0 || secondsSinceLastPoint < kTimeFilter {
                return false
            }
        }

        //avoid cached locations (before you start the locationManager)
        let secondsSinceManagerStarted = newLocation!.timestamp.timeIntervalSinceDate(startDate!)
        if secondsSinceManagerStarted < 0 {
            return false
        }

        return true
    }

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

        let newLocation = locations.last

        if isValidLocation(newLocation: newLocation, oldLocation:oldLocation) || oldLocation == nil {
            self.delegate?.locationControllerDidUpdateLocation(newLocation!)
            oldLocation = newLocation
        }

    }

}

class ViewController: UIViewController, MyLocationManagerDelegate {


    override func viewDidLoad() {
        super.viewDidLoad()

        let location = MyLocationManager()
        location.delegate = self

    }

    func locationControllerDidUpdateLocation(location: CLLocation) {
        //Api Call
    }

}